Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2003-06-03
2004-07-27
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S302000, C361S303000
Reexamination Certificate
active
06768630
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayer feedthrough capacitor used in a noise filter etc. designed not only to deal with noise of the common mode and noise of the differential mode, but also to reduce the equivalent serial inductance (ESL) more and thereby effectively eliminate noise in the high frequency band, more particularly one suitable for an information processing device or communications device.
2. Description of the Related Art
In recent years, the majority of information processing devices and communications devices have become digitalized. Further, along with the higher speeds of processing accompanying the improvements in information processing capabilities, there has been remarkable progress in raising the frequencies of the digital signals handled by these devices. Therefore, the noise produced from these devices also tends to increase more in the high frequency band. On the other hand, efforts are being made to make these devices more portable. Along with this, further reduction in the size and weight of these devices has become desired.
To deal with the noise, most electronic equipment use electronic devices able to prevent electromagnetic wave interference or suppress unnecessary voltage fluctuations. As these electronic devices, due to such a situation, electronic devices which are small in size, light in weight, and deal with noise in the high frequency band are being sought. As such electronic devices, in general, multilayer ceramic capacitors are currently being used.
In multilayer ceramic capacitors, however, the parasitic component, that is, the ESL, obstructs the noise eliminating effect in the high frequency band, so the effect has become insufficient along with the increasingly higher frequencies of the operating frequencies of electronic equipment. That is, capacitors having large ESLs such as the conventional multilayer ceramic capacitors are increasingly becoming unable to sufficiently handle the higher frequencies of recent years.
For example, as a conventional capacitor able to reduce the ESL, a multilayer type feedthrough capacitor (multilayer feedthrough capacitor) has been developized and is in general use. A multilayer feedthrough capacitor
110
according to the prior art will be described below based on
FIG. 12
to FIG.
15
.
The multilayer feedthrough capacitor
110
, as shown in
FIG. 13
, has an internal conductor
112
having branch parts
112
A and
112
B led out toward two facing side surfaces. A dielectric sheet
124
formed on its surface with an internal conductor
114
led out to two side surfaces different from the two side surfaces where the branch parts
112
A and
112
B are led out has stacked with it a dielectric sheet
122
formed on its surface with the internal conductor
112
. Dielectric sheets not formed with internal conductors are stacked above and below that stack in the stacking direction. This stack is then fired to form the stack
120
shown in FIG.
12
.
As shown in
FIG. 12
, two facing side surfaces of the stack
120
are formed with terminal electrodes
131
and
132
which are connected to the branch parts
112
A and
112
B of the internal conductor
112
. Further, the other two facing side surfaces of the stack
120
are formed with terminal electrodes
133
and
134
connected to the branch parts of the internal conductor
114
. As shown in
FIG. 14
, the terminal electrodes
131
and
132
can be connected to for example the ground side, while the terminal electrodes
133
and
134
can be connected to the signal transmission paths.
A circuit diagram for dealing with noise in the common mode and differential mode using this conventional multilayer feedthrough capacitor
110
is shown in FIG.
15
. As shown in
FIG. 15
, three multilayer feedthrough capacitors
110
are used to configure a circuit for reducing noise.
However, even in these multilayer feedthrough capacitors
110
, currents flow in the directions shown by the arrows in
FIG. 13
, so there is an ESL of a certain magnitude. Therefore, such conventional multilayer feedthrough capacitors
110
are increasingly becoming unable to handle the higher frequencies of recent years and capacitors able to reduce the ESL further are becoming required.
Further, to deal with the higher density mounting accompanying the smaller sizes of electronic equipment, demand is rising for array type multilayer capacitors combining a plurality of capacitors.
Note that in multilayer capacitors, it is known to make the shape of the pattern of the internal conductor a substantially T-shape as shown in Japanese Unexamined Patent Publication (Kokai) No, 59-29413 and Japanese Unexamined Patent Publication (Kokai) No. 3-37850. These publications, however, do not disclose the idea of passing currents in opposite directions in internal conductors adjacent in the stacking direction so as to reduce the ESL.
Further, as shown in Japanese Unexamined Patent Publication (Kokai) No. 2000-58376, the idea has been proposed of reducing the ESL by optimizing the ratio of dimensions of the internal conductor in the capacitor. Further, as shown in Japanese Examined Patent Publication (Kokoku) No. 6-58861, Japanese Unexamined Patent Publication (Kokai) No. 8-55758, and Japanese Unexamined Patent Publication (Kokai) No. 2001-189234, the idea is known of passing currents in the opposite directions in an internal conductor of a capacitor.
However, these publications do not disclose that it is possible to reduce the noise of both the common mode and the differential mode in a multilayer feedthrough capacitor and to further reduce the ESL so as to improve the effect of elimination of high frequency noise.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a multilayer feedthrough capacitor able to reduce both noise of the common mode and differential mode and able to further reduce the ESL so as to improve the effect of elimination of high frequency noise.
To achieve the above object, according to a first aspect of the present invention, there is provided a multilayer feedthrough capacitor comprising:
a first internal conductor arranged in a dielectric body,
an intermediate internal conductor arranged in the dielectric body and stacked with the first internal conductor via a ceramic layer,
a second internal conductor arranged in the dielectric body and stacked with the intermediate internal conductor via a ceramic layer,
a first terminal electrode formed at an outside surface of the dielectric body and connected to the first internal conductor,
a second terminal electrode formed at the outside surface of the dielectric body and connected to the second internal conductor, and
an intermediate terminal electrode formed at the outside surface of the dielectric body and connected to the intermediate internal conductor.
Preferably, the first internal conductor and the second internal conductor have currents passing through them in opposite directions.
Preferably, inside the dielectric body, the intermediate internal conductor is stacked between the first internal conductor and second internal conductor via the ceramic layers.
Preferably, the first internal conductor is formed with a pair of branch parts led out toward two opposite outside surfaces of the dielectric body, and each of the branch parts is connected to a pair of first terminal electrodes.
Preferably, the first internal conductor has a rectangular pattern slightly narrower than the ceramic layer forming the dielectric body, and
the pair of branch parts are formed at one end of the rectangular pattern in the longitudinal direction thereof.
Preferably, the second internal conductor is formed with a pair or branch parts led out toward two opposite outside surfaces of the dielectric body, and each of the branch parts is connected to each of a pair of second terminal electrodes.
Preferably, the second internal conductor has a rectangular pattern slightly narrower than the ceramic layer forming the dielectric body, and
the pair of branch parts are formed at one end
Dinkins Anthony
Oliff & Berridg,e PLC
TDK Corporation
LandOfFree
Multilayer feedthrough capacitor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multilayer feedthrough capacitor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multilayer feedthrough capacitor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3223290